The invention relates to a pressure relief system for a gyratory crusher having a crusher cone that is vertically adjustable by means of a hydraulic fluid assembly to control the size of the crushing gap.
Gyratory crushers with hydraulically-supported crusher cones are known in the prior art, for example Decker et al., U.S. Pat. No. 3,801,026 (1974). Also known in the prior art are pressure relief systems involving a hydraulic fluid assembly and an accumulator to receive displaced hydraulic fluid. Becker, U.S. Pat. No. 2,667,309 (1954).
Previously existing pressure relief systems have consisted of a single fluid assembly connected with one or more accumulators containing a bladder filled with a compressible gas. The fluid assembly is preset to a predetermined pressure, and when the pressure limit is exceeded, a valve is forced open, permitting free flow of the hydraulic fluid into the accumulators, thereby compressing the gas-filled bladders and increasing the pressure in the pressure relief fluid assembly. When the pressure in the crushing mechanism is reduced, the relief valve is forced shut, and the increased pressure in the pressure relief fluid assembly forces the hydraulic fluid from the accumulators back into the cone crusher support system by means of a metering check valve. The crusher cone is thereby raised to its initial crushing gap and normal operation continues.
A problem is often encountered with this type of pressure relief system due to the geometry of the crushing gap between the crusher cone and the outer crushing wall surrounding it. The gap is tapered in such a way that material entering at the top encounters a narrowing separation as it drops downward between the crusher cone and the surrounding wall. As a consequence, a piece of uncrushable foreign matter, which causes an increase in the crushing pressure and activates the pressure relief system, is able to drop only a small distance before becoming caught once more between the crusher cone and the surrounding wall. The increase in crushing pressure again activates the pressure relief system, but this time a greater pressure is required since the pressure relief system has not yet had sufficient time to recover from the first activation and is still at a higher pressure than normal. This sequence of events continues until the foreign matter drops out of the crusher, which may require as many as fifteen or more successive activations of the pressure relief system, each requiring a greater pressure than the preceding. As a result, both the crusher and pressure relief systems see successively larger pressure peaks, three times each second, resulting in vibration and ever greater stresses on the system.
An object of the present invention is to provide a pressure relief system for hydraulically-supported gyratory crushers which is not subject to increasingly large pressure peaks as a piece of uncrushable foreign matter is passed through the system.
Another object of the invention is to allow uncrushable foreign matter to pass through the crusher more easily, without requiring many successive activations of the pressure relief system.
A further object of the invention is to provide a quicker time response to increases in crushing pressure by attaching the pressure relief valve directly to the crusher, rather than communicating with the crusher by means of a pipe line.
Another object of the invention is to facilitate removal of the pressure relief valve for crusher maintenance, and to obviate the need to remove heavy and unwieldy pipes in order to get to the crusher mechanism.
Further details, features and advantages of the invention will be evident from the following detailed description, with reference to the accompanying drawings.